1. Field of the Invention
This invention relates in general to a video signal output apparatus capable of converting an input video format to a plurality of video formats and outputting the converted video formats.
2. Description of Related Art
In recent years, a video apparatus corresponding to a plurality of video formats is increasing due to the development of digital signal processing technology and the digitization of the video signals. Digital broadcasting is also increasingly popular and various media for recording digital video signals are also being developed. Therefore, from now on, tremendous demand for transmitting ends and receiving ends for the video signals will be increased.
The main formats used for the commercial broadcasting are 480i, 480p, 576i, 576p, 720p and 1080i, etc., for example. However, not all of the video signal output apparatus and the video display apparatus correspond to all the aforementioned formats.
Therefore, when apparatuses are connected, the combination of displayable video formats is more often restricted. Namely, a user has to know the video formats respectively corresponding to the video signal output apparatus and the video display apparatus, and the connectable video formats must be memorized. Moreover, when possessing a plurality of a video display apparatus and a video signal, there is a trouble that the video format for these apparatuses has to be reset whenever the connecting combination is changed.
For solving the above problem, Japanese Laid Open 2001-111914 (pages 3-5, and FIG. 1) provides, for example, a method which is described as follows. The video formats corresponding to the video display apparatus are automatically determined from the period of the horizontal deflection frequency. From the above determined video formats, the video signal output apparatus selects a suitable video format to output the video signals.
However, if the connected apparatus is not a CRT TV having a horizontal deviation circuit, this method is not useful. Namely, the above method cannot be applied to the recent increasingly popular liquid crystal display (LCD) TV and the plasma display panel (PDP) TV. In addition, when the user himself selects a video format, the connected apparatuses have to be reset respectively.
Conventionally, when video images are seen by connecting a video display apparatus and a video signal output apparatus corresponding to a plurality of video formats, the connectable image format has to be memorized. When the connected apparatuses are changed, there is a problem that the video format of these apparatuses needs to be reset.